Shift to mineral sunscreen poses formulation challenges

Bryan Moran, global skin care technical manager at Lubrizol Life Science Beauty, discusses how formulators can address a key trend in sun care

In the 1970s and 1980s, no lifeguard would hit the beach without a thick white coating of zinc oxide sunblock on their nose. It was effective but also unattractive and uncomfortable.

No-one, especially lifeguards, was sorry to see the thick zinc oxide (ZnO) and titanium dioxide (TiO2) mineral creams give way to lighter, easier-to-apply organic sunscreens. With the addition of avobenzone to organic sunscreens more than 20 years ago to protect against UVA rays, it seemed as if mineral sunscreens were a thing of the past.

However, recent concerns about the chemicals in organic sunscreens have manufacturers and consumers reconsidering mineral sunscreens and hybrid mineral-organic sunscreens. Ironically, a product created to protect against a long-unrecognised danger is now falling out of favour because of its own previously unrecognised risks. The concerns over organic sunscreens, including oxybenzone, avobenzone, octocrylene, homosalate and octinoxate, are sparking the shift back to mineral sunscreens i.e. ZnO and TiO2.

In response to consumer fears, the FDA, which regulates sunscreens as over-the-counter drugs in the US, has issued a number of regulations in the past few years. Most recently, in September 2021, the agency said it needed more time and data to take a position on the safety of sunscreen chemicals. The FDA left untouched a 2019 proposed rule that deemed only two of 16 common UV filters as generally recognised as safe and effective: ZnO and TiO2.

Two of the organic chemical compounds – aminobenzoic acid and trolamine salicylate – are proposed as being not safe and effective for sunscreen use. The other 12 remain under review. A final rule is expected later this year.

The need for direction became more urgent in January 2020, when the agency reported findings that six chemical UV filters are absorbed into the bloodstream more easily than previously known. It was careful to note, however, “absorption does not equal risk.”

In addition, concerns about possible benzene contamination prompted manufacturers to recall some sunscreen products while the retailer CVS halted sales of two after-sun products. Other scientists have called on the FDA to remove sunscreen that contains octocrylene for fear that it can degrade into benzophenone, a possible carcinogen.

Organic sunscreen chemicals are also under attack for the environmental harm they can cause coral reefs. Hawaii, the US Virgin Islands, Bonaire, Palau and other tropical locations have banned sunscreens containing reef-damaging chemicals. A National Academy of Sciences review of sunscreen chemicals’ environmental impact should be concluded this year, which could lead to further bans.

Given all that, it is not surprising that manufacturers are pivoting to mineral sunscreens and mineral-organic hybrids, which pose fewer of the environmental and health concerns of their organic counterparts.

A growing market

Sun care products took a hit during the pandemic, largely due to a decline in travel and outdoor activities. However, as travel resumes and borders reopen, the market is rebounding. Fortune Business Insights predicts that the global sun care market will reach $16.84 billion by 2027, up from $13.03 billion in 2019.

However, consumers are looking for more than just sun protection factor (SPF) and ‘reef-friendly’ claims from sun care products. They want multifunctional protection and the benefits previously limited to skin care products, such as hydration, protection against pollution, skin sensitivity, skin brightening, anti-ageing and more.

As a result, the line between sun care and skin care is blurring. Skin care manufacturers recognise this and are moving into the sun care realm, introducing skin care products that offer increasing levels of protection against the sun along with traditional skin care benefits.

That said, no-one wants to return to the days of thick sunscreens that leave a white residue. Years of using organic sunscreens have conditioned consumers to expect their sun care products to go on easily, have a pleasing texture and be invisible.

According to Lubrizol Life Science-Beauty (LLS Beauty) research, consumers rated oily and greasy texture, tacky residue and smell among their top objections to inorganic sunscreens. So the challenge to formulators is clear, if difficult: to develop safe, effective mineral or hybrid formulations that apply and feel like organic sunscreens.

While ZnO and TiO2 remain as the active ingredients, these new formulations will have to be enhanced by other ingredients that address the disadvantages that plagued the mineral sunscreens of old. They will not only have to be compatible with UV filters, but must also address the texture, application and whitening issues.

Formulation examples

LLS Beauty has a number of functional ingredients that can help provide the efficacy of mineral sunscreens with the benefits of organic products. These include the following: Matrifuse S-1 dispersant allows higher pigment loading applications with enhanced coverage, optical transparency and product sensory experience. It can effectively separate the agglomeration of pigment particles and significantly decrease the viscosity of dispersions, while allowing higher pigment loading, enhancing uniform coverage and boosting product sensory.

Avalure Flex-6 polymer is a non-ionic associative technology that provides film forming, pigment dispersion, emulsification and co-thickening. For sun care products, it provides a long-lasting, comfortable film and excellent water and sand adhesion resistance. This polymer’s multi-functionality allows for the replacement of emulsifiers and film formers in sunscreen formulations. In addition, it can disperse hydrophilic and hydrophobic ZnO and TiO2, while Schercemol esters enhance inorganic pigment dispersion for ZnO and TiO2.

Sunhancer Eco SPF booster is a naturally derived powder that increases SPF in the presence of UV filters. It showed an in vivo SPF boost up to 89%, depending on sunscreen combination, as well as absorption across the entire UV spectrum. In an in vivo test with a 10% ZnO, 5% TiO2 mineral sunscreen, the addition of 5% Sunhancer Eco SPF booster increased SPF by 35%.

Finally, Oilkemia 5S polymer is an oil-soluble rheology modifier that provides excellent thickening efficiency, clarity, suspension and stability, together with a non-tacky feel. For sun care, it has broad compatibility with UV filters, no whitening effect, a non-tacky feel and water resistance. It also boosts SPF. Anhydrous sunscreen film with Oilkemia 5S polymer boosted SPF 61% in vitro, compared to a sunscreen without the polymer.

Contact: LLS Beauty

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